The present embodiments relate to digital networks, and are more particularly directed to a multiple network configuration implementing redundancy both within each local network of the configuration as well as between the different remote networks of the configuration, where the redundancy is achieved using a redirect operation across dual media.
Data communication is a critical and everyday part of modern computing, and occurs through the use of various types of networks. Such data communication may be used for various reasons, such as business, science, telecommunications, personal, or entertainment. The span of such data communications may occur in different magnitudes. Particularly, in the network vernacular there has evolved notions of both local area networks (LANs) and wide area networks (WANs). As a generally stated distinction between the definition of a LAN and a WAN, a LAN is for more local communication of data such as within a small location, building, or complex, while a WAN is for communication of data across a greater distance which may be across a nation or even worldwide. Moreover, often a LAN is formed from only one or more locally connected networks, that is, in a manner where a given LAN host station on the network is only capable of communicating to those media which share the same "network" address which corresponds to the host address(es) of the given LAN host station, as is discussed in greater detail below. In contrast, a WAN often includes multiple networks where a given WAN host station may not only communicate to local hosts, but may further communicate via one or more routers with a remote network (and its host stations) where the remote network has a network address different than the network address corresponding to the host address(es) of the given WAN host station. In any event, the existence of networks for purposes of data communication is now very popular, and appears to be a way of life for the foreseeable future.
Various considerations of reliability arise along with the acceptance and proliferation of data communication among networks, one of which is the minimization of down time of a network. In other words, it is known in many types of data communication contexts that it is preferable to reduce or eliminate instances where one or more nodes attached to a network are unable to communicate with one or more of the other nodes also attached to the same network. In this regard, one attempt to minimize downtime of locally connected networks is through the use of so-called redundant solutions. Redundancy typically indicates that some type of resource associated with the network(s) is duplicated, and for reference and possible other purposes a first of these resources may be referred to as a primary resource while the second of these resources is referred to as a secondary resource. In the redundant system, if the primary resource becomes inoperative then the secondary resource is preferably quickly used in place of the primary resource, thereby minimizing or eliminating the chance to perceive the failure of the primary resource. Note that the actual resource or resources which are duplicated in this manner may depend on the particular context and, thus, could include repeating nodes, databases, network media, and still others as will be known by one skilled in the relevant art.
By way of further background, one type of prior art redundancy which has been used in the telecommunications industry has been in the context of an Ethernet LAN, and further involves the implementation of a fairly common network protocol known in the art as IP (internetwork protocol). Often the IP is mentioned as part of TCP/IP or UDP/IP. However, either of those two instances are actually a combination of two standards used in the protocol. For example, with respect to TCP/IP, the first protocol is TCP which is an abbreviation for transport control protocol. The second protocol is the IP introduced above. Although the name TCP/IP combines these two standards, in actuality the standards are implemented in an ordered level manner such that the TCP protocol is closer to the application level and the IP protocol is closer to the physical network connection level. In any event, TCP/IP and UDP/IP are well known and permit packets of information to be sent and received along different types of networks. Returning then to a discussion of the prior art IP approach, which is also detailed in greater fashion later, note that it provides two Ethernet interfaces for each node in the LAN thereby connecting each such node to redundant Ethernet cables. Consequently, assuming no failure of any node in the LAN, then each node may communicate to any other node on the LAN along either (or both) of the two Ethernet cables. However, if a failure occurs along one of the two routes of communication (e.g., a failure in an Ethernet cable), then a node may still communicate to other nodes along the other of the two Ethernet routes of communication. In various contexts such an approach has satisfactorily reduced the amount of network down time and provided valuable reliability to the users of the network.
While the prior art approach of the preceding paragraph provides various benefits, the present embodiments address various of its attributes which in some contexts may provide limitations. As a key example, the above-described approach is constrained to implementation for each single autonomous network, where typically that network is locally formed as a LAN. However, if a first such LAN is connected to one or more remote LANs to form a multiple network WAN, then the prior art approach does not comprehend, for a node in the first LAN, a fault in one of the redundant media in the remote LAN. Further, the prior art approach makes no provision for redundancy along the communication path between the two LANs. Clearly, the use of a WAN which includes multiple networks may be highly desirable or even necessary for various types of communications, with telecommunications as a key example. Thus, an approach which provides redundancy only within each autonomous network LAN may provide unacceptable or at least a severely restrictive limitation in some contexts.
To better understand some of the limitations of the above-described approach to an autonomous network using the IP standard, a brief discussion of IP address formats is now provided. More specifically, under the standards for IP, an IP address for a node on a network is formed by combining four integers typically represented in the following fashion: EQU Q.R.S.T
Ultimately at the machine level, each of the integers are represented in eight bit binary fashion and thus, provide four "bytes" which are also sometimes referred to as "octets." Thus, the IP address is a total of 32 bits (i.e., four bytes * 8 bits per byte). As binary values, therefore, the values of Q through T are each between 0 and 255. Thus, in decimal form, the same address may be represented as follows, with numeric ranges substituted for the above: EQU 0-255.0-255.0-255.0-255
Still further principles also apply to these addresses, such as the use of "class" identifiers for class A through class E networks based on the different permitted values of the various bytes of the address. For purposes of this document, a detailed explanation of such additional principles is not presented but instead deference is given to one skilled in the art.
In order to ensure an understanding of the above convention, the limitations of the prior art, and the inventive embodiments described later, note that all IP addresses are divisible into two portions, those being a host (or sometimes called a "node") address and a network address. The host address is some number of the least significant bits ("LSBs") of the address (i.e., those to the right of the value), while the network address is then the remaining most significant bits ("MSBs") of the address. For purposes of this document, therefore, and as is conventional in the art, when the term "network" is used it is intended to be defined as the combination of the medium and those network hosts that are connected to that medium and share this same network address. Thus, in the prior art approach described earlier, when it is stated that it is limited to a network, that indicates that only the hosts using that same network address benefit from that approach. Thus, to the extent a first such network is connected to a second network such as through routers or the like, the prior art approach does not permit the first network to perform its redundancy capability with respect to the second network. Lastly, and as also known in the art, note that the actual division of the total 32 bit IP address between a network address and a host address will vary based on certain implementation factors, such as the type of class of the network as well as the use of subnetting. These factors combine to form a so-called network mask which is a 32 bit value used in a logical operation on a bit-by-bit basis with an IP address for a given system-L As a result of this logical operation, the mask blocks or "masks" one portion of the IP address and thereby permits the other portion of the IP address to bypass the mask. These two portions are therefore separated in the manner introduced above, that is, in a group of the MSBs and a group of the LSBs of the IP address. The resulting MSBs form the network address, and the resulting LSBs form the host address.
Given the preceding explanation, note now that the limitation of the above-described approach to a single network provides a quantitative restriction on the number of nodes in the network (e.g., LAN) which may implement the approach. Particularly, assume for a given network that it is defined such that the three most significant bytes of each address form the network address and, thus, the least most significant byte remains to form host addresses for that network. As a result of the one byte of information available to distinguish among host addresses, there are at most 256 distinct values which may be represented. With only this restriction, only up to 256 node addresses may implement the prior art approach for such a network. Additionally, as detailed later, for each group of bits forming a host address, the values of all binary zeros and all binary ones are reserved and not available for use as a node address. Thus, in the present example there are actually only 254 node addresses available. Given this scenario, the above-described prior art redundancy approach is limited to 254 node addresses.
Note that the prior art constraint of a single network solution is not necessarily overcome simply by reducing the number of desired nodes to less than 254 (or less than whatever the number of host addresses are available given the breakdown of the IP address into a network address and a group of host addresses). In other words, there may be additional reasons to support multiple networks (e.g., in a WAN) rather than a single network and, again, the above-described prior art approach will not provide sufficient redundancy to multiple networks. For example, geographical considerations may require a WAN which is implemented by more than one network. As another example, given the introduction to IP concepts provided above, note further that messages submitted along a single network are received by all other nodes on the same network (although there may not be a response by one or many of those nodes). Consequently, if one of the nodes transmits some type of erroneous message or otherwise incurs a problem which is manifested on the network, then the operation of that one node may interfere with the operation of each of the remaining nodes which, by definition, are required to monitor that same network. Thus, a multiple network implementation may be desirable in order to permit numerous networks to interact with one another while avoiding this potential interference problem.
Given the above, the present inventor has appreciated the preceding limitations and provides below a multiple network configuration which implements redundancy between nodes both within each individual network of the configuration as well as between nodes on different networks within the configuration.